Bedside ultrasonography: Applications in critical care: Part I

Abstract

There is increasing interest in the use of ultrasound to assess and guide the management of critically ill patients. The ability to carry out quick examinations by the bedside to answer specific clinical queries as well as repeatability are clear advantages in an acute care setting. In addition, delays associated with transfer of patients out of the Intensive Care Unit (ICU) and exposure to ionizing radiation may also be avoided. Ultrasonographic imaging looks set to evolve and complement clinical examination of acutely ill patients, offering quick answers by the bedside. In this two-part narrative review, we describe the applications of ultrasonography with a special focus on the management of the critically ill. Part I explores the utility of echocardiography in the ICU, with emphasis on its usefulness in the management of hemodynamically unstable patients. We also discuss lung ultrasonography - a vastly underutilized technology for several years, until intensivists began to realize its usefulness, and obvious advantages over chest radiography. Ultrasonography is rapidly emerging as an important tool in the hands of intensive care physicians.

Keywords: Critical care; imaging; ultrasonography.

Figure 1

Probe location for basic echocardiographic views. (a) Apical, (b) parasternal, (c) subcostal

Figure 2

Right atrial and right ventricular dilatation in acute pulmonary embolism

Figure 3

Pericardial effusion seen as an echo-free space around the heart. Arrow depicts right atrial collapse

Figure 4

Diameter variation of the inferior vena cava with respiration. Maximum and minimum diameters are measured on M mode (IVC: Inferior vena cava; Max: Maximum diameter; Min: Minimum diameter)

Figure 5

Measurement of the velocity-time integral (VTI). The cursor is placed at the left ventricular outflow tract and interrogated with pulse wave Doppler. The resulting waveform is traced down to measure VTI

Figure 6

Bubble contrast echocardiographic study, showing a right to left shunt at the atrial level. Opacification is visible in the left atrium and left ventricle

Figure 7

Suggested algorithm for the evaluation and management of a hypotensive patient. LV: Left ventricle; RV: Right ventricle; RA: Right atrium; PE: Pulmonary embolism; IVC: Inferior vena cava; VTI: velocity time integral of the LV outflow tract; SLR: Straight leg raising test

Figure 8

The “lung point” sign seen at the confluence of the visceral and parietal pleura

Figure 9

(a) Pleural line (arrow) with normal lung below, (b) alveolar interstitial syndrome with several characteristic “B” lines seen radiating from the pleural line

Figure 10

Consolidated lung with “tissue like” echogenicity, resembling the liver. Arrows point to air bronchograms that brighten up during inspiration

Figure 11

Pleural effusion with the lung floating in fluid like “jelly fish”. Arrow points to the diaphragm